First reloading attempt; 9mm and need answers to COL variation

[seawash]

This is my first attempt reloading brass. I did a small batch of 50, 9mm: 25 at COL 1.140 and 25 at 1.145.

Equipment used was Hornady Lnl AP with Lee 4 Die set (seat and crimp separately). Did not use as “Progressiveâ€, I ran the brass in batches thru each die separately. Brass was not measured but all was Winchester. Bullets were Hornady 9mm 115 gn FMJ/RN ordered in bulk from mainstream supplier.

When I measured each round from base to tip, I discovered a wide variation in COL. I thought I screwed up, so I checked my caliper against another one, sorted the rounds by size, removed the die, set everything up again with a round that equaled 1.140 COL and reran 25. I did the same for the next 25 at 1.145. I ended up with the same variation. I did a Google search and discovered that due to variation in bullet manufacture some difference in COL would be expected, especially if measuring from base to tip.

For the 1.140 batch, the COL ranged from 1.136 to 1.144.

For the 1.145 batch, the COL ranged from 1.145 to 1.147.

I then grabbed a handful of bullets (125 out of a box of 500) and measured them. From base to tip, they ranged from .546 to .554, the most common size was .552 at only 31%. I have no idea if base to ogive is consistent, as I have no way to measure that.

Is this much variation in bullet size common or did I just have bad luck and end up with a box of misfits?

If bullets vary that much, and seating bullets deeper can lead to increased pressure, how are you supposed to follow a published recipe with a COL of 1.100, or 1.140, etc.?

Is it safe to assume that each bullet is seated to the same depth (from base to ogive) and the variation is only due to differences in the length of the tip?

Thanks

Seawash

[Jonnin]

I would think this is caused by some sort of variation in the press itself.

Typically the distance from the shell holder/base of the round to the top of the seating die is a constant. If there is no give in the press, every round should be the same OAL: longer slugs get pushed in more, shorter ones pushed in less, but they stop at that same distance for the same OAL.

That makes me think that your press allows you to slip past the hard stop a tiny bit sometimes, or inertial of really pushing the round in there fast, or something causes it? Or some other slight give in the press, a loose die or flexible C press frame?

I am not sure, but those are my gut feelings.

[Guest Lester Weevils]

Hi seawash

I get similar minor variation out of a dillon square deal b, but dunno why. Obviously a person would want to throw the lever "all the way" every time, but I think I do that.

Was thinking perhaps it could also have to do with variations in the brass length. I'm adjusted for "barely any" bell, and some cases get more bell than others, which may be that some cases are a tiny bit short and don't hardly hit the belling die at all, because it is adjusted to barely touch the brass anyway, for "just enough bell" to avoid shaving the bullets.

Had also wondered if there are brand-variances in the geometry of the case bases. Maybe some cases sit in the shell holder tighter, or maybe some cases tend to sit in the shell holder a little lower or higher, because of slight differences in the way the extraction groove is machined-in.

I ought to some time sort out cases of the same brand, which look like they were made about the same time (identical markings, etc) and see if that would tighten the variance in OAL. As long as the ammo goes bang and they fit in the chamber, am not gonna bother to trim the brass. But I don't know anything more about it than you do. Just another ignorant opinion.

[Jonnin]

I do not see how brass brand would change it (???). The distance from the bottom of the case to the top of the seating die should still be constant, making the OAL constant, right? Belling or crimping might have an effect --- maybe the crimp die could stretch it or push the round in our out a little, or the belling could be too deep and cause it to slip in a bit more, or something.... ????

I would say not to worry about it, but, I would be a hippocrite. I spent months fighting the OAL of my 223.

Edited June 21, 2012 by Jonnin

[Guest Lester Weevils]

Yes too much bell might allow the bullet to slip in a little too easy.

The explanation I have most faith in, on my situation, is minor variations in the geometry of the case bases, causing different cases to sit slightly high or low in the case holder. If a case rides a little low in the shell holder, then the OAL of the round would be a little long and vice-versa.

Eyeballing different brand cases, they don't all look "exactly the same" though they are all "close enough for rock'n'roll" to feed and go bang in the gun. The same could lead to slight differences in primer seating depth I suppose. Even with the RCBS hand priming tool which is very consistent, and with conformed primer pockets, some primers "barely go below flush". Which may mean that those cases will "move up slightly higher" in the shell holder so the ram can't quite push the primer as far into the hole. That tool has a stop in its motion so you couldn't "put the grip of death" on the thing and crush a primer flat in the bottom of the case.

I don't worry much about slight OAL variances in the rounds.

Edited June 21, 2012 by Lester Weevils

[Jonnin]

I am not getting the geometry thing. The bottom of all my 9mm cases are flat. They sit directly on the shell holder, flat. I measure them with the calipers across that same surface: still flat. What gemoetry other than flat are you seeing? The extractor ring varies, a bit, but that does not change the OAL or how my shell holder grasps it. I really do not understand what you are saying, but if that is the case, sure, different brass that sat in the holder differently, some with a gap and some flush, could do it, but ????? how does that happen??

Edited June 21, 2012 by Jonnin

[Guest Lester Weevils]

Hi Jonnin

In my square deal b press, it has a rotating shell holder with four grooved slots to hold four cases at a time. The 9mm cases ride in grooves in the slot, so they can't go too far in when pressed down, and they can't "pop out" when pressed up by priming. So if there is variation in the extraction ring geometry in the shell, I think they would have slightly different heights when "pushed down" and slightly different primer seating depth when "pushed up".

There could also be flex in the case holder, but one would think the flex would be about the same every time.

My RCBS hand primer has spring-loaded fingers that hold the 9mm cases by the groove, so its the same thing. Variances in the extraction groove could allow some shells to move up higher than others when the primer ram pushes "up" on the case.

Edited June 21, 2012 by Lester Weevils

[Jonnin]

Ah, that is very different from mine, I can see that. Mine is just a flat shell holder & the bottom of the case sits flat on it, and i see no way the brass could really have any effect.

[seawash]

All, thanks for the input. For the record, all primers were below flush and as this was my first attempt, I went slow and methodical- or as my wife tells me I was being anal. I don't think i was short stroking the lever either.

[Jonnin]

All, thanks for the input. For the record, all primers were below flush and as this was my first attempt, I went slow and methodical- or as my wife tells me I was being anal. I don't think i was short stroking the lever either.

You cannot be too careful with explosives, really. Slow is the perfect way to start, and to be honest, being "too comfortable" with explosives is probably bad (same as with guns, getting lax leads to problems!).

Not sure what else to say.... you could try sorting out 10 of the same brand of brass, see if that is the issue? Can't hurt.

[Guest Lester Weevils]

Ah, that is very different from mine, I can see that. Mine is just a flat shell holder & the bottom of the case sits flat on it, and i see no way the brass could really have any effect.

I need to go out in the shop and look more closely at my SDB shell holder to see if it is a reasonable theory for minor bullet seating variations. Am pretty sure it might be a reasonable theory for explaining some primers not wanting to seat any more than "barely flush" even with a deep primer pocket, but the design of my shell holder might be such that the downward "wiggle room" is just as restricted as with your shell holder.

[Guest nysos]

Ever thought it might be as simple as the locking ring on the dies has become looser from vibrations as you load? My dad uses lee dies and everytime I have loaded on his equipment after about 100 rounds, I recheck OAL and reset the dies because unless you really crank the crap out of the locking nut it loosens a tad. Since our loads change based off whatever bullet type we get that is on sale, we don't wrench the ring on too tight so that we can easily change it.

Try taking a dry erase marker and making a line on the outside of the die then reload a batch that way you can use it as a visual reference if it is backing itself out and the locking ring isn't doing the trick.

[frankmako]

you can drive yourself nuts over something like the "oal" of any reload you make. the numbers you show are so small and will not give you any problems. set your "oal" and crank out ammo. started reloading in 1973 and i have found it is best to setup the press/dies, lock them down and crank out ammo. quick recheck of all setting every 100 round, that is if you have good named brand equipment.

[seawash]

you can drive yourself nuts over something like the "oal" of any reload you make. the numbers you show are so small and will not give you any problems. set your "oal" and crank out ammo. started reloading in 1973 and i have found it is best to setup the press/dies, lock them down and crank out ammo. quick recheck of all setting every 100 round, that is if you have good named brand equipment.

Thanks, that's what I wanted to hear. With the variation in bullet length, I just wanted to make sure that this was not out of line. I've seen posts on Al Gore's internet, that your COL variance shouldn't be more than .001, but my bullets vary by .008 so I don't see how I can get that to .001.

[RichardS]

This is just a guess but it is very possible that the bullets are not shaped exactly the same (slightly different ogives) and your bullet seater meets them in slightly different places. If you seater is like mine it does not push on the tip of the bullet but rather somewhere further down and where it hits depends on the shape of the bullet.

I also use a Hornady LnL and a Lee 4 die set for 9mm. I get a few thousandths difference in OAL within a batch so my results are similar to yours. I've not kept good enough records to know if certain brands/types of bullets are more consistent than others, but I do remember they all varied by a few thousandths. I've used Hornady 115g XTP, Remington 124g Golden Saber, Berry's plated 124g HP, Missouri 125g RN and CN, Dardas 122g RNFP, and Dardas 124g and 125g RN.

nysos has a good point above, I do get dies loosening once in a while. The LnL bushings can turn a bit as well so keep and eye on them, I use a wrench to snug them down. I've seen posts on other forums saying that Hornady will send you a shim that is supposed to keep the LnL busings in place better. So if you have this problem you could give them a call. The marker idea is great, I am going to start doing that to get a visual when something loosens.

Check the large allen head bold that holds the shellplate to the press, mine loosens once in a while. This probably would not affect OAL but will affect primer seating depth and how the completed rounds eject.

I also noticed the fit between my ram and subplate was not perfect and the subplate could tilt a few thou. I put some shim stock in between them and reassembled and it seems rock solid now. Again, I heard Hornady will send you a shim if you call them, I had some shim stock available so did not call. This slight tilt could affect OAL because the subplate is what the base of the shell is sitting.

Last though is to keep a small brush (old toothbrush works for me) handy and wipe off any powder that spills and gets on/under the shellplate. While very small, I'm sure a bit of squashed powder could throw things off by a thou or two.

Edited June 25, 2012 by RichardS